Method of manufacturing semiconductor devices having contact plugs overlapping associated bitline structures and contact holes

ABSTRACT

A semiconductor device can include a plurality of landing pads arranged according to a layout on a substrate, wherein a cross-sectional shape of each of the landing pads has a diamond shape so that opposing interior angles of the diamond shape are equal to one another and adjacent interior angles of the diamond shape are unequal to one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/288,228, filed Oct. 7, 2016, which itself is a divisional of U.S.patent application Ser. No. 14/754,040, filed Jun. 29, 2015, whichitself claims the benefit of Korean Patent Application No.10-2014-0109042, filed on Aug. 21, 2014, in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein intheir entireties by reference.

BACKGROUND

The inventive concept relates to semiconductor devices and methods ofmanufacturing the same, and more particularly, to semiconductor deviceshaving contact plugs and methods of manufacturing the same.

A high degree of integration of semiconductor devices in electronicdevices can lead to decreased design rules for elements of thesemiconductor devices. When forming contact plugs for connecting upperelements and lower elements in highly integrated semiconductor devices,bridging between the contact plugs, or necking (i.e., thinning of aportion of the contact plugs) may occur, which can lead to adeterioration in reliability of the semiconductor devices.

SUMMARY

Embodiments according to the invention can provide semiconductor deviceshaving contact plugs overlapping associated bit line structures andcontact holes and methods of forming the same. Pursuant to theseembodiments, a semiconductor device can include a plurality of landingpads arranged according to a layout on a substrate, wherein across-sectional shape of each of the landing pads has a diamond shape sothat opposing interior angles of the diamond shape are equal to oneanother and adjacent interior angles of the diamond shape are unequal toone another.

In some embodiments according to the inventive concept, a first diagonalof the diamond shape that bisects a first pair of the opposing interiorangles has a different length than a second diagonal of the diamondshape that bisects a second pair of the opposing interior angles. Insome embodiments according to the inventive concept, each of the landingpads is included in a contact plug that is electrically connected to anunderlying active area of the substrate.

In some embodiments according to the inventive concept, wherein an upperportion of each of the landing pads is electrically connected to a lowerelectrode of a respective capacitor. In some embodiments according tothe inventive concept, each of the landing pads overlaps a bit linestructure and an adjacent contact hole associated with the respectivecapacitor.

In some embodiments according to the inventive concept, a portion ofeach of the landing pads that overlaps the contact hole partially fillsthe contact hole so that a remaining portion of the contact holeadjacent a neighboring bit line structure is unoccupied by the portionof each of the landing pads that overlaps the contact hole. In someembodiments according to the inventive concept, a first and a second ofthe landing pads are electrically connected to the underlying activearea in the substrate. In some embodiments according to the inventiveconcept, the first and second landing pads are positioned asymmetricallyrelative to the underlying active area.

In some embodiments according to the inventive concept, a semiconductordevice can include a substrate having a plurality of active areas, aplurality of bit line structures formed on the substrate, eachcomprising a bit line extending in a first direction and a bit linespacer layer extending along two opposing side surfaces of the bit line,a plurality of contact holes spaced apart from one another in alengthwise direction in a space between ones of the plurality of bitline structures, a plurality of first contact plugs filling respectivebottom portions of the plurality of contact holes and electricallyconnected with respective ones of the plurality of active areas, and aplurality of second contact plugs electrically connected with respectiveones of the plurality of first contact plugs, and on the respective onesof the plurality of bit line structures, wherein the plurality of secondcontact plugs are laid out on respective upper surfaces of the pluralityof bit line structures in a hexagonal array structure and wherein eachof the second contact plugs has a diamond-shaped cross-sectional plane.

In some embodiments according to the inventive concept, the plurality ofsecond contact plugs each comprise a body portion and an extensionportion extending from the body portion into a respective one of theplurality of contact holes and the diamond-shaped cross-sectional planeis included in the body portion.

In some embodiments according to the inventive concept, a diagonal lineof the body portion with respect to the diamond-shaped cross-sectionalplane extends in the first direction. In some embodiments according tothe inventive concept, lengths of two diagonal lines of the body portionwith respect to the diamond-shaped cross-sectional plane are differentfrom each other. In some embodiments according to the inventive concept,the cross-sectional plane of the body portion has a round-edged diamondshape.

In some embodiments according to the inventive concept, a plurality ofbody portions are alternately arranged to alternately overlap twoopposing side surfaces of one of the bit line structures in the firstdirection. In some embodiments according to the inventive concept, eachbody portion overlaps a portion of a respective one of the plurality ofbit line structures and overlaps a portion of a respective one of theplurality of contact holes, in a direction perpendicular to a mainsurface of the substrate.

In some embodiments according to the inventive concept, three of fouredges of the diamond-shaped cross-sectional plane of the body portionoverlap the respective one of the plurality of bit line structures. Insome embodiments according to the inventive concept, the body portionsof two of the plurality of second contact plugs that correspond to oneof the plurality of active areas, have different size areas that overlapthe corresponding one of the plurality of active areas.

In some embodiments according to the inventive concept, a semiconductordevice can include a substrate having a plurality of active areas, aplurality of bit line structures formed on the substrate, eachcomprising a bit line extending in a first direction and a bit linespacer layer extending along two side surfaces of the bit line, aplurality of first contact plugs spaced apart from one another in alengthwise direction of a space between ones of the plurality of bitline structures, and electrically connected with respective ones of theplurality of active areas, and a plurality of second contact plugselectrically connected with respective ones of the plurality of firstcontact plugs and on respective ones of the plurality of bit linestructures, wherein two of the plurality of second contact plugscorresponding to one of the plurality of active areas, have differentsize areas overlapping the one of the plurality of active areas in adirection that is perpendicular to a main surface of the substrate.

In some embodiments according to the inventive concept, the plurality ofsecond contact plugs overlap respective portions of the plurality of bitline structures and respective portions of the plurality of firstcontact plugs in the direction perpendicular to the main surface of thesubstrate, and respective portions of the plurality of second contactplugs, which are arranged on upper surfaces of the respective ones ofthe plurality of bit line structures to have an area that overlaps theplurality of bit line structures, which is greater than an area thereofoverlapping the plurality of first contact plugs.

In some embodiments according to the inventive concept, a method ofmanufacturing a semiconductor device, can include preparing a substratehaving a plurality of active areas, forming a plurality of bit linestructures on the substrate and each comprising a bit line extending ina first direction and a bit line spacer layer extending along twoopposing side surfaces of the bit line, forming a plurality of contactholes spaced apart from one another along a lengthwise direction of aspace between the plurality of bit line structures, and a plurality offirst contact plugs filling bottom portions of the plurality of contactholes and electrically connected with the plurality of active areas,forming a conductive material layer to fill the plurality of contactholes and to cover the plurality of bit line structures, forming aplurality of first line patterns extending to form a diagonal line withrespect to the first direction and arranged on the conductive materiallayer, and a plurality of second line patterns arranged on the pluralityof first line patterns and crossing the plurality of first linepatterns, and forming a plurality of second contact plugs eachelectrically connected with respective ones of the plurality of firstcontact plugs, by etching the conductive material layer using theplurality of first line patterns and the plurality of second linepatterns as an etch mask.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the inventive concept will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a layout of a semiconductor device according to someembodiments;

FIG. 2 is a cross-sectional view of some elements of a semiconductordevice according to some embodiments;

FIG. 3 is a layout illustrating a state in which a first contact plug isformed in methods of manufacturing semiconductor devices, according tosome embodiments;

FIGS. 4A and 4B are cross-sectional views of some elements in a state inwhich a first contact plug is formed in methods of manufacturingsemiconductor devices, according to some embodiments;

FIG. 5 is a layout illustrating a state in which a conductive materiallayer is formed in methods of manufacturing semiconductor devices,according to some embodiments;

FIGS. 6A and 6B are cross-sectional views of some elements in a state inwhich a conductive material layer is formed in methods of manufacturingsemiconductor devices, according to some embodiments;

FIGS. 7A and 7B are layouts illustrating a state in which a first linepattern is formed in methods of manufacturing semiconductor devices,according to some embodiments;

FIGS. 8A and 8B are cross-sectional views of some elements in a state inwhich a first line pattern is formed in methods of manufacturingsemiconductor devices, according to some embodiments;

FIGS. 9A through 9C are layouts illustrating a state in which a secondline pattern is formed in methods of manufacturing semiconductordevices, according to some embodiments;

FIGS. 10A and 10B are cross-sectional views of some elements in a statein which a second line pattern is formed in methods of manufacturingsemiconductor devices, according to some embodiments;

FIGS. 11A and 11B are cross-sectional views illustrating etching aconductive material layer in methods of manufacturing semiconductordevices, according to some embodiments;

FIG. 12 is a layout illustrating a state in which a second contact plugis formed in methods of manufacturing semiconductor devices, accordingto some embodiments;

FIGS. 13A and 13B are cross-sectional views of some elements in a statein which a second contact plug is formed in methods of manufacturingsemiconductor devices, according to some embodiments;

FIG. 14 is a flowchart illustrating a process of forming a secondcontact plug in methods of manufacturing semiconductor devices,according to some embodiments;

FIG. 15 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 16 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 17 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 18 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 19 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 20 is a layout of some elements of a semiconductor device accordingto some embodiments;

FIG. 21 is a block diagram of a semiconductor device according to someembodiments;

FIG. 22 is a diagram of a system including a semiconductor deviceaccording to some embodiments; and

FIG. 23 is a diagram of a memory card including a semiconductor deviceaccording to some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, the inventive concept is described with reference to theaccompanying drawings, in which exemplary embodiments of the inventiveconcept are shown. Like reference numerals in the drawings denote likeelements, and a repeated explanation may not be given of overlappingfeatures or like elements. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

These inventive concept may, however, be embodied in different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough and complete and fully conveys the inventive concept to thoseof ordinary skill in the art.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer, or section from another region, layer, orsection. Thus, a first element, component, region, layer, or sectiondiscussed below could be termed a second element, component, region,layer, or section without departing from the teachings of exemplaryembodiments. For example, a first element could be termed a secondelement, and, similarly, a second element could be termed a firstelement, without departing from the scope of exemplary embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which exemplary embodiments belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

When an exemplary embodiment may be implemented differently, a specificprocess order may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order.

In the drawings, variations from the shapes of the illustrations as aresult, for example, of manufacturing techniques and/or tolerances, areto be expected. Thus, exemplary embodiments should not be construed aslimited to the particular shapes of regions illustrated herein but maybe to include deviations in shapes that result, for example, frommanufacturing.

Throughout this specification, the term “angle” denotes an acute angle,unless otherwise defined or shown. For example, in the expressions “amajor axis has a first angle with respect to a first direction,” and “aline pattern extends by a second angle with respect to a firstdirection,” the first and second angles denote the acute angle.

In this specification, the term “overlap” denotes to overlap in adirection perpendicular to a main surface of a substrate, unlessotherwise defined or shown.

FIG. 1 is a layout of a semiconductor device 1 according to someembodiments.

Referring to FIG. 1, the semiconductor device 1 includes a plurality ofactive areas ACT. Each of the plurality of active areas ACT may have arelatively long island shape with a minor axis and a major axis. Each ofthe plurality of active areas ACT may have a major axis extending in adirection diagonal with respect to a first direction (direction x). Aplurality of word lines WL extend in parallel with one another along asecond direction (direction y) across the plurality of active areas ACT.The plurality of word lines WL may be arranged at equal intervals. Onthe plurality of word lines, a plurality of bit lines BL extend inparallel with one another along the first direction (direction x) whichis perpendicular to the second direction (direction y). Each of theplurality of bit lines BL and a bit line spacer layer extending alongtwo side surfaces of the bit line may form a bit line structure BLS.That is, the bit line structure BLS excluding the bit line BL maycorrespond to the bit line spacer layer. The bit line structures BLS mayextend in parallel with one another along the first direction (directionx).

The plurality of bit lines BL are connected with the plurality of activeareas ACT through a plurality of direct contacts DC. Each of theplurality of active areas ACT may be electrically connected with arespective one of the plurality of direct contacts DC.

A plurality of buried contacts BC may be formed in a region between twoadjacent bit line structures BLS from among the plurality of bit linestructures BLS. In some embodiments, the plurality of buried contacts BCmay be arranged spaced apart from one another along a lengthwisedirection of the space between the two adjacent bit line structures BLS,that is, the first direction (direction x). A portion of the spacebetween the two adjacent bit line structures BLS, in which the pluralityof buried contacts BC are not formed, may be filled with a plurality ofinsulating patterns 165. The plurality of buried contacts BC may have amatrix array structure in which the plurality of buried contacts BC arearranged in series along the first direction (direction x) and thesecond direction (direction y). In some embodiments, the plurality ofburied contacts BC may be arranged at equal intervals along the firstdirection (direction x).

The plurality of buried contacts BC may electrically connect a storagenode ST which is a lower electrode of a capacitor to the plurality ofactive areas ACT. Each of the plurality of active areas ACT may beelectrically connected with two buried contacts BC.

A plurality of landing pads LP may be arranged on the bit line structureBLS such that each of the plurality of landing pads LP is alsoelectrically connected with each of the plurality of buried contacts BC.The plurality of landing pads LP may electrically connect the storagenode ST which is a lower electrode of a plurality of capacitors with theplurality of active areas ACT. The storage node ST may be electricallyconnected with the plurality of active areas ACT though the plurality ofburied contacts BC and the plurality of landing pads LP.

One from among the plurality of buried contact BC and one from among theplurality of landing pad LP, corresponding to each other, may bereferred to as a contact plug. The buried contact BC and the landing padLP may be referred to as a first contact plug BC and a second contactplug LP, respectively. That is, the first contact plug BC and the secondcontact plug LP may electrically connect the storage node ST with theplurality of active areas ACT.

A portion LP1 of the second contact plug LP may be arranged on an uppersurface of the bit line structure BLS. The portion of the second contactplug LP that is arranged on the upper surface of the bit line structureBLS may be referred to as a body portion LP1 and the other portion maybe referred to as an extension portion (refer to LP2 of FIG. 2).

A cross-sectional plane of the body portion LP1 of the second contactplug LP may have a diamond shape. The body portion LP1 of the secondcontact plug LP may have a diagonal line with respect to thediamond-shaped cross-sectional plane, the diagonal line (refer to DN1 ofFIG. 16) extending in the first direction (direction x extending betweenopposing corners). The body portion LP1 of the second contact plug LPmay have the other diagonal line with respect to the diamond-shapedcross-sectional plane, the other diagonal line extending (refer to DN2of FIG. 16) in the second direction (direction y extending betweenopposite corners). Lengths of the two diagonal lines of the body portionLP1 of the second contact plug LP with respect to the diamond-shapedcross-sectional plane may be different from each other. Thecross-sectional plane of the body portion LP1 of the second contact plugLP may have a round-edged diamond shape.

The body portion LP1 of the second contact plug LP may have an areaoverlapping the bit line structure BLS, which is greater than an areaoverlapping the first contact plug BC. Three from among four edges ofthe diamond shape of the cross-sectional plane of the body portion LP1of the second contact plug LP may overlap the bit line structure BLS.

The body portions LP1 of the plurality of second contact plugs LP may bearranged to have a hexagonal array structure. The body portions LP1 ofthe plurality of second contact plugs LP may be alternately arrangedsuch that the body portions LP1 alternately overlap two side surfaces ofthe bit line structure BLS along the first direction (direction x).

The body portions LP1 of two second contact plugs LP corresponding to(overlapping) one from among the plurality of active areas ACT, may havedifferent size areas overlapping the one from among the plurality ofactive areas ACT. The body portions LP1 of two second contact plugs LPcorresponding to (overlapping) one from among the plurality of activeareas ACT, may be arranged on different bit line structures BLS. Thebody portions LP1 of two second contact plugs LP corresponding to(overlapping) one from among the plurality of active areas ACT, may bearranged on two adjacent bit line structures BLS, respectively. The bodyportions LP1 of two second contact plugs LP corresponding to(overlapping) one from among the plurality of active areas ACT, may bearranged such that the body portions LP1 overlap corresponding sidesurfaces of different bit line structures BLS.

The body portions LP1 of two second contact plugs LP corresponding to(overlapping) one from among the plurality of active areas ACT, mayoverlap an identical side surface of the one from among the plurality ofactive areas ACT, from among two side surfaces thereof, the two sidesurfaces being based on a major axis of the one from among the pluralityof active areas ACT.

A column formed by the body portions LP1 along an extension lineconnecting the body portions LP1 may be arranged along a direction thatis different from a direction of the major axis of the one from amongthe plurality of active areas ACT.

Two first contact plugs BC corresponding to one from among the pluralityof active areas ACT, may have a symmetrical shape based on a center ofthe one from among the plurality of active areas ACT. Two second contactplugs LP corresponding to one from among the plurality of active areasACT, may have an asymmetrical shape based on a center of the one fromamong the plurality of active areas ACT.

The plurality of second contact plugs LP may be arranged to form a rowin the second direction (direction y) which is perpendicular to thefirst direction (direction x). The plurality of second contact plugs LPmay be arranged to overlap corresponding side surfaces of (the samedirection) of the plurality of bit line structures BLS.

Each of a plurality of storage nodes ST may be arranged on the secondcontact plug LP as a hexagonal array structure. An area of a lowersurface of the storage node ST may be greater than an area of an uppersurface of the second contact plug LP.

Although elements around edges may be omitted or cut in the layout ofFIG. 1 and later layouts, this is only for convenience of illustration.The arrangement and shape of the elements are not limited thereto.

FIG. 2 is a cross-sectional view of some elements of a semiconductordevice according to an exemplary embodiment. FIG. 2 is a cross-sectionalview taken along a line II-II′ of FIG. 1.

Referring to FIGS. 1 and 2, a device separating layer 112 is formed on asubstrate 110 and a plurality of active areas 110A is defined on thesubstrate 110 by the device separating layer 112. Each of the pluralityof active areas 110A may have a relatively long island shape with aminor axis and a major axis, as each of the plurality of active areasACT illustrated in FIG. 1.

The substrate 110 may include, for example, silicon (Si). Alternatively,the substrate 110 may include a semiconductor element, such as germanium(Ge), or a compound semiconductor, such as silicon carbide (SiC),gallium arsenide (GaAs), indium arsenide (InAs), and indium phosphide(InP). Alternatively, the substrate 110 may have a silicon on insulator(SOI) structure. For example, the substrate 110 may include a buriedoxide (BOX) layer. The substrate 110 may include a conductive area, forexample, a well doped with impurities or a structure doped withimpurities.

The device separating layer 112 may be formed of, for example, amaterial including at least one selected from a silicon oxide layer, asilicon nitride layer, and a silicon oxynitride layer. The deviceseparating layer 112 may be formed as a single layer formed of one typeof insulating layer, a double layer formed of two types of insulatinglayers, or a multi-layer formed of a combination of at least three typesof insulating layers. For example, the device separating layer 112 maybe formed of two different types of insulating layers. For example, thedevice separating layer 112 may be formed of a silicon oxide layer and asilicon nitride layer. For example, the device separating layer 112 maybe formed as a triple layer formed of a silicon oxide layer, a siliconnitride layer, and a silicon oxide layer.

After the device separating layer 112 is formed, a plurality of wordlines (refer to WL of FIG. 1) are formed. The word lines WL will bedescribed in detail with reference to FIG. 4B.

A source/drain area may be formed on some upper portions of theplurality of active areas 110A. To form the source/drain area, impurityions may be loaded onto the substrate 110.

An insulating layer pattern 130 in which a plurality of openings areformed may be formed on the substrate 110. The insulating layer pattern130 may be formed to have a thickness of about 200 Å to about 400 Å. Theinsulating layer pattern 130 may include silicon oxide.

A plurality of direct contacts DC which may be electrically connectedwith the plurality of active areas 110A are formed by filling theplurality of openings formed in the insulating layer pattern 130 with aconductive material.

A plurality of bit line structures 160 extending in parallel with oneanother are formed on the insulating layer pattern 130 and the pluralityof direct contacts DC. Each bit line structure 160 includes a bit line140, an insulating capping layer 152 covering an upper surface of thebit line 140, and a bit line spacer layer 156 covering side walls of thebit line 140 and the insulating capping layer 152. The plurality of bitlines 140 may be electrically connected with the plurality of directcontacts DC.

In some embodiments, the bit line 140 may include at least one materialselected from a semiconductor doped with impurities, a metal, conductivemetal nitride, and metal silicide. In some embodiments, the bit line 140may be formed as a stack of a first conductive layer 142 and a secondconductive layer 144. The first conductive layer 142 may be formed of,for example, doped polysilicon. The second conductive layer 144 may beformed of, for example, a metal or metal nitride, such as W or TiN.Metal silicide, for example, may be further formed between the firstconductive layer 142 and the second conductive layer 144.

The insulating capping layer 152 may be formed of, for example, asilicon nitride layer. A thickness of the insulating capping layer 152may be greater than a thickness of the bit line 140.

The bit line spacer layer 156 may be formed of, for example, a siliconoxide layer, a silicon nitride layer, air, or a combination thereof. InFIG. 2, it is illustrated that the bit line spacer layer 156 is formedas a single layer. However, the present inventive concept is not limitedthereto, and the bit line spacer layer 156 may be formed as a doublelayer, triple layer or more.

The plurality of bit line structures 160 may extend in parallel with oneanother along the first direction (direction x), as the plurality of bitline structures BLS illustrated in FIG. 1.

A line shaped space, a width of which along the second direction(direction y) is defined by the bit line spacer 156, remains betweeneach adjoining pair of the plurality of bit line structures 160. Aplurality of insulating patterns filling the space between eachadjoining pair of the plurality of bit line structures 160 and defininga contact hole CH are formed. The plurality of insulating patternsdenote insulating patterns 165 formed to fill the space between theplurality of bit line structures BLS of FIG. 1 excluding a portion inwhich the first contact plug BC is formed. The contact hole CHcorresponds to a portion of the space between the plurality of bit linesstructures BLS of FIG. 1, in which the first contact plug BC is formed.

The contact hole CH may extend to the plurality of active areas 110Athrough the space between the plurality of bit line structures 160 toexpose the plurality of active areas 110A.

The contact hole CH may be filled with a conductive material to form thefirst contact plug BC. The conductive material may be formed of, forexample, doped polysilicon. Alternatively, the conductive material mayinclude a barrier layer covering an inner wall of the contact hole CHand a conducive layer filling the contact hole CH on the barrier layer.Here, the barrier layer may be formed as a stack of Ti/TiN, and theconductive layer may be formed of doped polysilicon, a metal, metalsilicide, conductive metal nitride, or a combination thereof. A portionof the conductive material filling an upper portion of the contact holeCH is removed to form a first contact plug BC filling a lower portion ofthe contact hole CH and electrically connected with the active area110A. Metal silicide, for example, may be further formed between thefirst contact plug BC and the active area 110A.

Then, the plurality of second contact plugs LP electrically connectedwith the plurality of first contact plugs BC, respectively, and arrangedon the bit line structures 160 are formed. Each of the plurality ofsecond contact plugs LP may be formed of the body portion LP1 which is aportion arranged on an upper surface of the bit line structure 160, andthe extension portion LP2 which extends from the body portion LP1 intothe contact hole CH to cover the first contact plug BC. The body portionLP1 of the second contact plug LP may have the diamond-shapedcross-sectional plane, as illustrated in FIG. 1. Edges of the bodyportion LP1 of the second contact plug LP may be partially removed in amanufacturing process so that the cross-sectional plane of the bodyportion LP1 may have a round-edged diamond shape, as illustrated in FIG.1.

In some embodiments, a metal silicide layer may be arranged between thefirst contact plug BC and the second contact plug LP.

The second contact plug LP may be formed of a conductive barrier layer212A covering the bit line structure 160 and the first contact plug BC,and a plug conductive layer 214A covering the conductive barrier layer212A. The conductive barrier layer 212A may be formed as, for example, astack of Ti/TiN. The plug conductive layer 214A may be formed of, forexample, doped polysilicon, a metal, metal silicide, conductive metalnitride, or a combination thereof.

That is, the second contact plug LP may be formed of the conductivebarrier layer 212A and the plug conductive layer 214A. Also, the secondcontact plug LP may be formed of the body portion LP1 and the extensionportion LP2.

Each of the plurality of second contact plugs LP may be formed of thebody portion LP1 arranged on an upper surface of a bit line structure160 from among two bit line structures 160 facing each other in thecontact hole CH, and the extension portion LP2 extending from the bodyportion LP1 into the contact hole CH to cover the bit line spacer layer156 of the bit line structure 160 from among two bit line structures 160facing each other in the contact hole CH.

The extension portion LP2 may fill an upper portion of the contact holeCH, which is not filled with the contact plug BC. The extension portionLP2 may extend from an uppermost portion of a bit line spacer layer 156from among two bit line spacer layers 156 facing each other downwardinto the contact hole CH to the first contact plug BC. The extensionportion LP2 may extend through the first contact plug BC to a locationwhich is lower than an uppermost portion of the other bit line spacerlayer 156 from among the two bit line spacer layers 156. Thus, twoadjacent second contact plugs LP may be separated from each other, andmay be electrically connected with different first contact plugs BC.That is, the two adjacent second contact plugs LP may be separated fromeach other by a spacing formed by the portion of the contact hole CH,which is not filled with the extension portion LP2.

A plurality of capacitor lower electrodes 400 may be formed on theplurality of second contact plugs LP. The plurality of capacitor lowerelectrodes 400 may be arranged to have a hexagonal array structure likethe storage nodes ST illustrated in FIG. 1. An area of a lower surfaceof each of the plurality of capacitor lower electrodes 400 may begreater than an area of an upper surface of the second contact plug LP.The capacitor lower electrodes 400 may be electrically connected withthe active areas 110A through the second contact plug LP and the firstcontact plug BC.

Although it is illustrated in FIG. 2 that a capacitor lower electrode400 has a cylinder shape, it is not limited thereto. The capacitor lowerelectrode 400 may adopt all of various known shapes of lower electrodes,such as a pillar shape. A capacitor dielectric layer and a capacitorupper electrode may be sequentially formed on the capacitor lowerelectrode 400 to form a capacitor.

FIGS. 3 through 14 are layouts and cross-sectional views for describingmethods of manufacturing semiconductor devices, according to someembodiments.

FIG. 3 is a layout of a state in which the first contact plug BC can beformed, in methods of manufacturing semiconductor devices in someembodiments.

FIGS. 4A and 4B are cross-sectional views of some elements in the statein which the first contact plug BC is formed in methods of manufacturingthe semiconductor device in some embodiments, taken along a lineIVa-IVa′ and a line IVb-IVb′ of FIG. 3, respectively.

Referring to FIGS. 3 and 4B, the device separating layers 112 are formedon the substrate 110, and the plurality of active areas 110A are definedon the substrate 110 by the device separating layers 112.

A plurality of word line trenches 118 are formed on the substrate 110.The plurality of word line trenches 118 extend in parallel with oneanother. Each of the plurality of word line trenches 118 may have a lineshape crossing the plurality of active areas 110A.

After the plurality of word line trenches 118 are cleared, a pluralityof gate dielectric layers 120, a plurality of word lines 122, and aplurality of buried insulating layers 124 are sequentially formed in theplurality of word line trenches 118.

The plurality of word lines 122 may extend in parallel with one anotheralong the second direction (direction y of FIG. 3), as the word lines WLillustrated in FIG. 3.

In some embodiments, after the plurality of word lines 122 are formed,impurity ions may be injected onto the substrate 110 at two sides of theplurality of word lines 122 to form a source/drain region in some upperportions of the plurality of active areas 110A. In some embodiments, theinjection of impurity ions for forming the source/drain region may beperformed before the plurality of word lines 122 are formed.

An upper surface of each of the plurality of word lines 122 is locatedat a level lower than a level of an upper surface of the substrate 110(i.e., buried). A lower surface of each of the plurality of word lines122 may have a convex-concave shape, and a saddle FinFET may be formedin the plurality of active areas 110A. In some embodiments, theplurality of word lines 122 are formed of at least one material selectedfrom Ti, TiN, Ta, TaN, W, WN, TiSiN, and WSiN.

The gate dielectric layer 120 may be formed of at least one selectedfrom a silicon oxide layer, a silicon nitride layer, a siliconoxynitride layer, oxide/nitride/oxide (ONO), and a high-k dielectricfilm having a higher dielectric constant than a silicon oxide layer. Forexample, the gate dielectric layer 120 may have a dielectric constant ofabout 10 to about 25. In some embodiments, the gate dielectric layer 120may be formed of at least one material selected from HfO, HfSiO, HfON,HfSiON, LaO, LaAlO, ZrO, ZrSiO, ZrON, ZrSiON, TaO, TiO, BaSrTiO, BaTiO,SrTiO, YO, AlO, and PbScTaO. For example, the gate dielectric layer 120may be formed of HfO₂, Al₂O₃, HfAlO₃, Ta₂O₃, or TiO₂.

An upper surface of the plurality of buried insulating layers 124 may belocated at a level approximately the same as the level of the uppersurface of the substrate 110. The buried insulating layer 124 may beformed of a silicon oxide layer, a silicon nitride layer, a siliconoxynitride layer, or a combination thereof.

After the plurality of word lines 122 and the plurality of buriedinsulating layers 124 are formed, the insulating layer pattern 130 inwhich the plurality of openings are formed may be formed on thesubstrate 110. The insulating layer pattern 130 may be formed to have athickness of about 200 Å to about 400 Å. The insulating layer pattern130 may include silicon oxide. For example, the insulating layer pattern130 may be formed of tetraethylorthosilicate (TEOS), high density plasma(HDP), or boro-phospho silicate glass (BPSG).

The plurality of direct contacts DC, which may be electrically connectedwith the plurality of active areas 110A, are formed by filling theplurality of openings formed in the insulating layer pattern 130 with aconductive material. In the process of forming the insulating layerpattern 130 in which the plurality of openings are formed, a portion ofthe substrate 110, which is exposed through the plurality of openings,may be also removed, and the plurality of direct contacts DC may extendinto the substrate 110 in the openings. A portion of the active area110A, which contacts the direct contact DC, may be a source region.

The plurality of bit line structures 160 extending in parallel with oneanother are formed on the insulating layer pattern 130 and the pluralityof direct contacts DC. The bit line structure 160 includes the bit line140, the insulating capping layer 152 covering an upper surface of thebit line 140, and the bit line spacer layer 156 covering side walls ofthe bit line 140 and the insulating capping layer 152. The plurality ofbit lines 140 may be electrically connected with the plurality of directcontacts DC.

In some embodiments, the bit line 140 may include at least one materialselected from a semiconductor doped with impurities, a metal, conductivemetal nitride, and metal silicide. In some embodiments, the bit line 140may be formed as a stack of the first conductive layer 142 and thesecond conductive layer 144. The first conductive layer 142 may beformed of, for example, doped polysilicon. The second conductive layer144 may be formed of, for example, a metal or metal nitride, such as Wor TiN. Metal silicide, for example, may be further formed between thefirst conductive layer 142 and the second conductive layer 144.

The plurality of direct contacts DC may be formed together with thefirst conductive layer 142 and may be integral with the first conductivelayer 142 (which can provide a unitary structure). For example, theplurality of direct contacts DC may be the conductive material withwhich the plurality of openings are filled to form the first conductivelayer 142. In some embodiments, the plurality of direct contacts DC andthe first conductive layer 142 may be formed separately. For example,the first conductive layer 142 may be formed separately after theplurality of direct contacts DC are formed.

The insulating capping layer 152 may be formed of, for example, asilicon nitride layer. The insulating capping layer 152 may be thickerthan the bit line 140.

The bit line spacer layer 156 may be formed of, for example, a siliconoxide layer, a silicon nitride layer, air, or a combination thereof. InFIG. 4A, it is illustrated that the bit line spacer layer 156 is formedas a single layer. However, the present inventive concept is not limitedthereto, and the bit line spacer layer 156 may be formed as a doublelayer, a triple layer or more.

In some embodiments, first, a conductive layer for forming a bit line,and an insulating layer covering the conductive layer for forming a bitline are formed on the insulating layer pattern 130, in order to formthe plurality of bit line structures 160. The insulating layer may bethicker than the conductive layer for forming a bit line. After theplurality of capping layers 152 are formed by patterning the insulatinglayer, the conductive layer for forming a bit line is etched by usingthe plurality of insulating capping layers 152 as an etch mask, in orderto form the plurality of bit lines 140. The plurality of bit lines 140may extend in parallel with one another along the first direction(direction x of FIG. 3), as the bit lines BL illustrated in FIG. 3.

Next, the plurality of bit line spacer layers 156 covering the sidewalls of the plurality of bit lines 140 and the plurality of insulatingcapping layers 152 are formed to form the plurality of bit linestructures 160.

The plurality of insulating patterns 165 defining the contact hole CHare formed in spaces between the plurality of bit line structures 160.In some exemplary embodiments, the plurality of insulating patterns 165may be formed of a nitride layer, an oxide layer, or a combinationthereof. In some exemplary embodiments, in order to form the pluralityof insulating patterns 165, first an insulating layer filling the spacesbetween the plurality of bit line structures 160 is formed, and theinsulating layer is etched back by an etchback or a chemical mechanicalpolishing (CMP) process to expose an upper surface of the plurality ofbit line structures 160 so that portions of the insulating layer remainin the spaces between the plurality of bit line structures 160. Then, amask pattern of a predetermined shape is formed, and a portion of theinsulating layer is removed by using the mask pattern as an etch mask,in order to form the plurality of insulating patterns 165 defining theplurality of contact holes CH. Then, the mask pattern is removed.

After the plurality of insulating patterns 165 are formed, a portion ofthe substrate 110 is etched through lower surfaces of the plurality ofcontact holes CH to expose the substrate 110 at the lower surfaces ofthe plurality of contact holes CH. In some embodiments, when a materiallayer formed together with the bit line spacer layer 156 and/or theinsulating layer pattern 130 remain at the lower surfaces of theplurality of contact holes CH after the plurality of insulating patterns156 are formed, a portion of the material and/or the insulating layerpattern 130 may be etched through the lower surfaces of the plurality ofcontact holes CH, and then, the portion of the substrate 110 may beetched.

In some embodiments, a metal silicide layer may be formed on the surfaceof the substrate 110, which is exposed through the lower surfaces of theplurality of contact holes CH. For example, the metal silicide layer maybe formed of cobalt silicide. However, according to the presentinventive concept, the metal silicide layer is not limited thereto, andmay be formed of a material selected from various types of metalsilicide.

Then, a conductive layer for forming a contact, which fills theplurality of contact holes CH and covers the plurality of bit linestructures 160, is formed. In some embodiments, the conductive layer forforming a contact may be formed of doped polysilicon. In someembodiments, the conductive layer for forming a contact may include abarrier layer covering inner walls of the plurality of contact holes CHand a conductive layer filling the plurality of contact holes CH on thebarrier layer. Here, the barrier layer may be a formed as a stack ofTi/TiN, and the conductive layer may be formed of doped polysilicon, ametal, metal silicide, conductive metal nitride, or a combinationthereof.

An upper surface of the bit line structure 160 is exposed by removing aportion of the conductive layer for forming a contact, and the firstcontact plug BC is formed by forming a space in an upper portion of thecontact hole CH.

The plurality of first contact plugs BC may extend in a verticaldirection in the plurality of contact holes CH, that is, in a directionwhich is perpendicular (direction z) to a main surface of the substrate110, and may have an upper surface which is lower than the upper surfaceof the bit line structure 160. That is, the plurality of first contactplugs BC may fill some lower portions of the plurality of contact holesCH. The first contact plug BC may have a horizontal cross-sectional areaof a first size, which is defined by a size of the contact hole CH.

The method of manufacturing the device separating layer 112, the activeareas 110A, the word line trenches 118, the gate dielectric layers 120,the word lines 122, the buried insulating layers 124, the insulatinglayer patterns 130, the direct contacts DC, the bit line structures 160,the insulating patterns 165, the contact holes CH, and the first contactplugs BC is described with reference to FIGS. 3 through 4B. However, thepresent inventive concept is not limited thereto. The method thereof mayvary including manufacturing the first contact plug BC having an uppersurface lower than an upper surface of the bit line structure 160.

FIG. 5 is a layout illustrating a state in which a conductive materiallayer 210 is formed in methods of manufacturing the semiconductor devicein some embodiments.

FIGS. 6A and 6B are cross-sectional views of some elements in the statein which the conductive material layer 210 is formed in methods ofmanufacturing the semiconductor device in some embodiments, taken alonga line VIa-VIa′ and a line VIb-VIb′ of FIG. 5, respectively.

Referring to FIGS. 5 through 6B, the conductive material layer 210filling the plurality of contact holes CH and covering the plurality ofbit line structures 160 is formed. In some embodiments, the conductivematerial layer 210 may include a barrier layer 212 covering inner wallsof the plurality of contact holes CH, and the plurality of bit linestructures 160, and a conductive layer 214 for forming a landing plug,which fills the contact hole CH on the barrier layer 212. Here, thebarrier layer 212 may be formed as a stack of Ti/TiN and the conductivelayer 214 for forming a landing plug may be formed of doped polysilicon,a metal, metal silicide, conductive metal nitride, or a combinationthereof. For example, the conductive layer 214 for forming a landingplug may be formed of a metal, such as W.

FIGS. 7A and 7B are layouts illustrating a state in which a plurality offirst line patterns 310 are formed in methods of manufacturing thesemiconductor device in some embodiments. In detail, FIG. 7B is a layoutof FIG. 7A, in which some elements of FIG. 7A are omitted.

FIGS. 8A and 8B are cross-sectional views of some elements in the statein which the plurality of first line patterns 310 are formed in methodsof manufacturing the semiconductor device in some embodiments, takenalong a line VIIIa-VIIIa′ and a line VIIIb-VIIIb′ of FIG. 7A,respectively.

Referring to FIGS. 7A through 8B, the plurality of first line patterns310 extending as a diagonal line with respect to an extension directionof the bit line structure BLS, that is, with respect to the firstdirection (direction x) are formed on the conductive material layer 210.The plurality of first line patterns 310 extend in parallel with oneanother as the diagonal line with respect to the first direction(direction x). The plurality of first line patterns 310 may be arrangedat equal intervals.

The plurality of first line patterns 310 may have a first pitch P1. Theplurality of first line patterns 310 may be obtained by a doublepatterning technology (DPT) from a mother pattern which is formed by aphotolithography process such that the mother pattern has a pitch P1 awhich is greater than the first pitch P1.

In some embodiments, the plurality of first line patterns 310 may beformed by self aligned double patterning (SADP). In some embodiments,the plurality of first line patterns 310 may be formed by self alignedreverse patterning (SARP).

Here, the SADP denotes forming the plurality of first line patterns 310by using (as an etch mask) a son pattern which is formed by self alignedpatterning between the mother pattern formed by the photolithographyprocess and spacers formed at a side wall of the mother pattern. TheSARP denotes forming the plurality of first line patterns 310 by using(as an etch mask) the spacers formed at the side wall of the motherpattern formed by the photolithography process.

The plurality of first line patterns 310 may be formed of, for example,polysilicon, oxide, nitride, oxynitride, or a carbon-based layer. Thecarbon-based layer may be formed of, for example, an amorphous carbonlayer (ACL) or a carbon based spin-on hardmask (C—SOH) layer. However,the present inventive concept is not limited thereto.

The plurality of first line patterns 310 may be obtained by a processusing a mother pattern formed by a photolithography process to have apitch that is twice the first pitch P1. For example, the plurality offirst line patterns 310 may be obtained by the DPT, or by a quadruplepattern technology (QPT), from a mother pattern which is formed by aphotolithography process to have a pitch that is four times the firstpitch P1.

Referring to FIG. 7B, each of the plurality of active areas ACT may havea major axis extending along a direction which is diagonal with respectto the first direction (direction x). The major axis of the active areaACT may have a first angle θ1 with respect to the first direction(direction x). Here, the first angle θ1 denotes an acute angle formed bythe major axis of the active area ACT and the first direction (directionx).

Each of the plurality of first line patterns 310 may extend by a secondangle θ2 with respect to the first direction (direction x). Here, thesecond angle θ2 denotes an acute angle formed by the extension directionof the first line patterns 310 and the first direction (direction x).

The plurality of first line patterns 310 may extend in the diagonaldirection with respect to the first direction (direction x) such thatthe second angle θ2 is greater than the first angle θ1. That is, thefirst angle θ1 is greater than 0° and less than the second angle θ2.

FIGS. 9A through 9C are layouts illustrating a state in which aplurality of second line patterns 320 are formed in methods ofmanufacturing semiconductor devices according to some embodiments. Indetail, FIGS. 9B and 9C are layouts of FIG. 9A, in which some elementsof FIG. 9A are omitted.

FIGS. 10A and 10B are cross-sectional views of some elements in thestate in which the plurality of second line patterns 320 are formed inmethods of manufacturing semiconductor devices according to someembodiments. FIGS. 10A and 10B are cross-sectional views taken along aline Xa-Xa′ and a line Xb-Xb′ of FIG. 9A, respectively.

Referring to FIGS. 9A through 10B, the plurality of second line patterns320 extending by forming a diagonal line with respect to the extensiondirection of the bit line structure BLS, that is, with respect to thefirst direction (direction x), and crossing the plurality of first linepatterns 310, are formed on the conductive material layer 210 on whichthe plurality of first line patterns 310 are formed. The plurality ofsecond line patterns 320 extend in parallel with one another by formingthe diagonal line with respect to the first direction (direction x). Theplurality of second line patterns 320 may be arranged at equalintervals.

The plurality of second line patterns 320 may have a second pitch P2.The plurality of second line patterns 320 may be obtained by a doublepatterning technology (DPT) from a mother pattern which is formed by aphotolithography process to have a pitch P2 a which is greater than thesecond pitch P2.

In some embodiments, the plurality of second line patterns 320 may beformed by self aligned double patterning (SADP). In some embodiments,the plurality of second line patterns 320 may be formed by self alignedreverse patterning (SARP). The plurality of second line patterns 320 maybe formed of, for example, polysilicon, oxide, nitride, oxynitride, or acarbon-based layer. However, the present inventive concept is notlimited thereto.

The plurality of second line patterns 320 may be obtained by a processusing a mother pattern formed by a photolithography process to have apitch that is twice the second pitch P2. For example, the plurality offirst line patterns 310 may be obtained by the DPT, or by a quadruplepattern technology (QPT), from a mother pattern which is formed by aphotolithography process to have a pitch that is four times the secondpitch P1.

Referring to FIG. 9B, the major axis of the active area ACT may have thefirst angle θ1 with respect to the first direction (direction x). Eachof the plurality of second line patterns 320 may extend by a third angleθ3 with respect to the first direction (direction x). Here, the thirdangle θ3 denotes an acute angle formed by the extension direction of theplurality of second line patterns 320 and the first direction (directionx).

The plurality of second line patterns 320 may extend in the diagonaldirection with respect to the first direction (direction x) such thatthe third angle θ3 is greater than the first angle θ1. That is, thefirst angle θ1 may be greater than 0° and less than the third angle θ3.

Referring to FIG. 9C, the plurality of first line patterns 310 and theplurality of second line patterns 320 may cross each other. Theplurality of first line patterns 310 and the plurality of second linepatterns 320 may form diagonal lines extending by the same angle withrespect to the first direction (direction x). That is, the plurality offirst line patterns 310 and the plurality of second line patterns 320may extend by the second angle θ2 and the third angle θ3, respectively,with respect to the first direction (direction x). Here, the secondangle θ2 and the third angle θ3 may be the same angle.

Referring to FIGS. 9B and 9C, the first angle θ1 may be greater than 0°and less than the second angle θ2 and the third angle θ3.

Referring to FIG. 9C again, portions of the plurality of first linepatterns 310, crossed by the plurality of second line patterns 320, mayhave a hexagonal array structure with respect to a main surface of thesubstrate 110 (refer to FIGS. 10A and 10B). The portions of theplurality of first line patterns 310, crossed by the plurality of secondline patterns 320, may have a diamond shaped cross-sectional plane wherenot all interior angles in the diamond shape are equal to one another.

The plurality of first line patterns 310 and the plurality of secondline patterns 320 may be formed such that the portions of the pluralityof first line patterns 310, crossed by the plurality of second linepatterns 320, overlap (or span) a portion of the bit line structure BLSand a portion of the contact hole CH in a direction perpendicular to themain surface of the substrate 110 (refer to FIGS. 10A and 10B).

The plurality of first line patterns 310 and the plurality of secondline patterns 320 may be formed such that at least a portion of a spacein which a first space 310S (which is a space among the plurality offirst line patterns 310) and a second space 320S (which is a space amongthe plurality of second line patterns 320) cross each other overlap thefirst contact plug BC in the direction perpendicular to the main surfaceof the substrate 110 (refer to FIGS. 9C, 10A and 10B). Then, in aprocess of forming the second contact plug LP (refer to FIG. 1A) throughthe space in which the first space 310S and the second space 320S crosseach other, the plurality of second contact plugs LP may be separatedfrom one another. That is, the first contact plug BC may overlap each ofthe portion of the plurality of first line patterns 310, crossed by theplurality of second line patterns 320, and the portion of the space inwhich the first space 310S and the second space 320S cross each other,in the direction perpendicular to the main surface of the substrate 110(refer to FIGS. 10A and 10B).

FIGS. 11A and 11B are cross-sectional views for describing a process ofetching the conductive material layer 210 in methods of manufacturingsemiconductor devices in some embodiments according to the invention,taken along a line Xa-Xa′ and a line Xb-Xb′ of FIG. 9A, respectively.

Referring to FIGS. 9A through 10B, 11A, and 11B, the conductive materiallayer 210 is etched by using the plurality of first line patterns 310and the plurality of second line patterns 320 as an etch mask.

In the etching of the conductive material layer 210, exposed uppersurfaces of the plurality of first line patterns 310 and the pluralityof second line patterns 320 may be also removed. Here, an etching speedof the plurality of first line patterns 310 and the plurality of secondline patterns 320 may be less than an etching speed of the conductivematerial layer 210, or a thickness of the plurality of first linepatterns 310 and the plurality of second line patterns 320 may begreater than a thickness of the conductive material layer 210, so thatthe plurality of first line patterns 310 and the plurality of secondline patterns 320 may function as the etch mask and may at leastpartially remain after etching.

Since the plurality of second line patterns 320 are formed on theplurality of first line patterns 310, the upper surface of the pluralityof second line patterns 320 is completely exposed. Thus, in the etchingand removing of the conductive material layer 210, the plurality ofsecond line patterns 320 may be also removed. Until the plurality ofsecond line patterns 320 are completely removed, portions of theconductive material layer 210, exposed through the space in which thefirst space 310S and the second space 320S cross each other, may beetched. Even if the plurality of second line patterns 320 are completelyremoved, the portions of the plurality of first line patterns 310,crossed by the plurality of second line patterns 320, may not be removedand may remain. Here, the other portions of the plurality of first linepatterns 310, not crossed by the plurality of second line patterns 320,may be completely removed.

In this process, the portions of the conductive material layer 210 thatare exposed by the plurality of first line patterns 310 and the secondline patterns 320, may be removed to expose a portion of the uppersurface of the bit line structure 160.

FIG. 12 is a layout illustrating a state in which the second contactplug LP is formed in methods of manufacturing semiconductor devices insome embodiments.

FIGS. 13A and 13B are cross-sectional views of some elements in thestate in which the second contact plug LP is formed in methods ofmanufacturing semiconductor devices in some embodiments, taken along aline XIIIa-XIIIa′ and a line XIIIb-XIIIb′ of FIG. 12, respectively.

Referring to FIGS. 12 through 13B, the second contact plug LP is formedby the etching process of the conductive material layer 210 (refer toFIG. 11A). After the second contact plug LP is formed, a portion of thefirst line pattern 310 (refer to FIG. 11A) remaining on the secondcontact plug LP may be removed. The etching process of the conductivematerial layer 210 for forming the second contact plug LP may beperformed before the first contact plug BC is exposed. Thus, the secondcontact plug LP may completely cover an upper surface of the firstcontact plug BC.

The second contact plug LP may be formed of the conductive barrier layer212A and the plug conductive layer 214A covering the conductive barrierlayer 212A. The conductive barrier layer 212A and the plug conductivelayer 214A denote a remaining portion of the barrier layer 212 and aremaining portion the conductive layer 214 for forming a landing plug,illustrated in FIG. 10A, respectively, after the etching of theconductive material layer 210.

The second contact plug LP may extend from the upper surface of the bitline structure 160 downward into the contact hole CH to electricallyconnect with the first contact plug BC. The portion of the secondcontact plug LP, arranged on the upper surface of the bit line structureBLS, may be referred to as the body portion LP1, and the portion of thesecond contact plug LP in the contact hole CH, may be referred to as theextension portion LP2.

Since the body portion LP1 remains according to the portions that crossone another to provide the plurality of first line patterns and theplurality of second line patterns 320, the diamond-shapedcross-sectional plane may be provided for the body portion LP1 asillustrated in FIG. 9C. However, edges of the diamond shape may bepartially removed during the etching process, and thus, thecross-sectional plane of the body portion LP1 of the second contact plugLP may have a round-edged diamond shape. When the edges of the diamondshape are subjected to greater etching, however, the cross-sectionalplane of the body portion LP1 of the second contact plug LP may have anoval shape.

Next, the plurality of capacitor lower electrodes 400 may be formed onthe plurality of second contact plugs LP, as illustrated in FIG. 2.

In the semiconductor device according to some embodiments, the pluralityof second contact plugs LP are separated from one another simultaneouslyby the formation of the second contact plug LP. Thus, bridging betweenthe plurality of second contact plugs LP may be prevented. Also, sincethe second contact plug LP completely covers the upper surface of thefirst contact plug BC, sufficient low contact resistance may be obtainedbetween the first contact plug BC and the second contact plug LP. Also,since the second contact plug LP is integrally formed at once, extendingfrom the bit line structure BLS to the first contact plug BC, neckingmay be prevented from occurring on the second contact plug LP.

The present inventive concept is not limited to the method of formingthe second contact plug LP. For example, the etching process using theplurality of first line patterns 310 (refer to FIG. 9A) and theplurality of second line patterns 320 (refer to FIG. 9A) crossing theplurality of first line patterns 310, may also be applied in forming theplurality of storage nodes ST arranged to have the hexagonal arraystructure, as illustrated in FIG. 1.

FIG. 14 is a flowchart illustrating the process of forming the secondcontact plug LP in methods of manufacturing semiconductor devices insome embodiments. In detail, FIG. 14 is a flowchart illustrating methodsof forming semiconductor devices, illustrated in FIGS. 5 through 13B.

Referring to FIGS. 5 through 13B, and 14, the substrate 110 on which theactive areas 110A or ACT, the word lines 122 or WL, the direct contactsDC, the bit line structure 160 s or BLS, the contact holes CH, and thefirst contact plugs BC are formed is prepared in operation S10.

The conductive material layer 210 filling the plurality of contact holesCH and covering the plurality of bit line structures 160 is formed onthe substrate 110, in operation S100.

The plurality of first line patterns 310 having the first pitch P1 areformed on the conductive material layer 210 by a double patterningprocess from the mother pattern formed by a photolithography process tohave the pitch that is at least twice that of the first pitch P1, inoperation S200.

The plurality of second line patterns 320 having the second pitch P2 areformed on the conductive material layer 210 by a double patterningprocess from the mother pattern formed by a photolithography process tohave the pitch that is at least two times greater than the second pitchP2, in operation S300.

The plurality of second contact plugs LP electrically connected with theplurality of first contact plugs BC, respectively, are formed by etchingthe conductive material layer 210 by using the plurality of first linepatterns 310 and the plurality of second line patterns 320 as an etchmask, in operation S400.

FIG. 15 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 15 is a layout of FIG. 1, in which some elements of FIG. 1are omitted.

Referring to FIG. 15, the semiconductor device 1 includes the pluralityof active areas ACT. Each of the plurality of active areas ACT may havea relatively long island shape with a minor axis and a major axis. Eachof the plurality of active areas ACT may have a major axis extending inthe diagonal direction with respect to the first direction (directionx).

The plurality of buried contacts BC, that is, the plurality of firstcontact plugs BC, may have a matrix array structure which is arranged inseries along the first direction (direction x) and the second direction(direction y). In some embodiments, the plurality of first contact plugsBC may be arranged at equal intervals in the first direction (directionx). One active area ACT may be electrically connected with two firstcontact plugs BC.

The plurality of landing pads LP, that is, the plurality of secondcontact plugs LP, may be electrically connected with the plurality offirst contact plugs BC. The body portions LP1 of the plurality of secondcontact plugs LP may be arranged to have a hexagonal array structure.

The body portion LP1 of the second contact plug LP may have a diamondshaped cross-sectional plane. The body portion LP1 of the second contactplug LP may have a diagonal line with respect to the diamond-shapedcross-sectional plane, the diagonal line extending along the firstdirection (direction x). The body portion LP1 of the second contact plugLP may have another diagonal line with respect to the diamond-shapedcross-sectional plane, the diagonal line extending along the seconddirection (direction y). The two diagonal lines of the body portion LP1of the second contact plug LP with respect to the diamond-shapedcross-sectional plane may have different lengths. The cross-sectionalplane of the body portion LP1 of the second contact plug LP may have around-edged diamond shape.

The body portion LP1 of the second contact plug LP may overlap a portionof the contact hole CH. That is, the body portion LP1 of the secondcontact plug LP may overlap a portion of the first contact plug BCfilling the contact hole CH.

FIG. 16 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 16 is a layout of one active area of FIG. 1 and the firstand second contact plugs BC and LP corresponding to the active area.

Referring to FIG. 16, the semiconductor device 1 includes the activearea ACT. The active area ACT may have a relatively long island shapewith a minor axis and a major axis. The active area ACT may have a majoraxis extending along a diagonal direction with respect to the firstdirection (direction x).

The body portion LP1 of the second contact plug LP may have a diamondshaped cross-sectional plane. The body portion LP1 of the second contactplug LP may have a round-edged diamond shaped cross-sectional plane.

The body portion LP1 of the second contact plug LP may have a diagonalline DN1 with respect to the diamond-shaped plane cross-section, thediagonal line extending along the first direction (direction x), andanother diagonal line DN2 extending along the second direction(direction y). A first length D1 and a second length D2 of the twodiagonal lines DN1 and DN2 of the body portion LP1 of the second contactplug LP, respectively, with respect to the diamond-shapedcross-sectional plane, may be different from each other. In someembodiments, the first length D1 may be greater than the second lengthD2.

As described above, since the edges of the diamond shape may bepartially removed during the etching process, the body portion LP1 ofthe second contact plug LP may have a round-edged diamond shapedcross-sectional plane. Also, when the edges of the diamond shape aresubjected to additional etching, the cross-sectional plane of the bodyportion LP1 of the second contact plug LP may have an oval shape. Inthis case, a major axis of the oval shape may be along the firstdirection (direction x).

The active area ACT may be electrically connected with two first contactplugs BC corresponding to the active area ACT. The active area ACT maybe electrically connected with two second contact plugs LP correspondingto the active area ACT. Each of the two second contact plugs LPcorresponding to the active area ACT may be electrically connected withthe active area ACT through each different one of the two first contactplugs BC corresponding to the active area ACT.

The body portions LP1 of the two second contact plugs LP correspondingto (overlapping) the active area ACT may have different size areasoverlapping the active area ACT. A first body portion LP1 a and a secondbody portion LP1 b, that is, the body portions LP1 corresponding to theactive area ACT, may have a first area OVa and a second area OVb,respectively, which overlap the active area ACT. The first area OVa andthe second area OVb may have different values.

The active area ACT may have a major axis ACT-LX extending along adiagonal direction with respect to the first direction (direction x).The first body portion LP1 a and the second body portion LP1 b,corresponding to the active area ACT, may overlap an identical sidesurface ACT-S1 of the active area ACT, from among two side surfacesACT-S1 and ACT-S2 thereof, the two side surfaces being based on themajor axis ACT-LX of the active area ACT.

Each of the two first contact plugs BC corresponding to the active areaACT may overlap a different side surface ACT-S1 or ACT-S2, based on themajor axis ACT-LX of the active area ACT.

The two first contact plugs BC corresponding to the active area ACT mayhave a symmetrical shape based on the center of the active area ACT.Here, the center of the active area ACT denotes a planar center of theactive area ACT. The two first contact plugs BC corresponding to theactive area ACT may have a 180° rotational symmetry based on the centerof the active area ACT. The two second contact plugs LP corresponding tothe active area ACT may have an asymmetrical shape based on the centerof the active area ACT. The two second contact plugs LP corresponding tothe active area ACT may have a shape which is shifted toward a differentdirection from the direction of the major axis ACT-LX of the active areaACT.

The first body portion LP1 a of the body portions LP1 of the two secondcontact plugs LP corresponding to the active area ACT, and the firstcontact plug BC connected with the first body portion LP1 may overlapdifferent side surfaces ACT-S1 and ACT-S2 based on the major axis ACT-LXof the active area ACT. The second body portion LP1 b of the bodyportions LP1 of the two second contact plugs LP corresponding to theactive area ACT, and the first contact plug BC connected with the secondbody portion LP1 b may overlap the identical side surface ACT-S1 basedon the major axis ACT-LX of the active area ACT.

The second body portion LP1 b, which overlaps the identical side surfaceACT-S1 of the active area ACT with the first contact plug BC connectedwith the second body portion LP1 b, from among the body portions LP1corresponding to the active area ACT, may have a smaller area OVboverlapping the active area ACT than an area OVa of the first bodyportion LP1 a, which overlaps the different side surface ACT-S1 orACT-S2 to the first contact plug BC.

FIG. 17 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 17 is a layout of one active area of FIG. 1, the first andsecond contact plugs BC and LP corresponding to the active area, andportions of the bit line structures BLS.

Referring to FIG. 17, the semiconductor device 1 includes the activearea ACT, the bit line structures BLS, the first contact plugs BC, andthe second contact plugs LP.

The first and second body portions LP1 a and LP1 b may be arranged ondifferent (adjacent) bit line structures BLS. The first and second bodyportions LP1 a and LP1 b may be arranged to overlap corresponding sidesurfaces of the different bit line structures BLS. In some embodiments,the two second contact plugs LP may be arranged on two adjacent bit linestructures BLS, respectively.

FIG. 18 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 18 is a layout of one bit line structure BLS of FIG. 1, andthe body portions LP1 of the second contact plugs LP, which are formedon the bit line structure BLS.

Referring to FIG. 18, the semiconductor device 1 includes the bit linestructure BLS and the second contact plugs LP. The second contact plugsLP may be alternately arranged (i.e., staggered) such that the secondcontact plugs LP alternately overlap opposing side surfaces BLS-L andBLS-R of the bit line structure BLS in the first direction (directionx). The body portions LP1 may be alternately arranged to overlap theopposing surfaces BLS-L and BLS-R of the bit line structure BLS in thefirst direction (direction x).

FIG. 19 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 19 is a layout of the body portions LP1 of the secondcontact plugs LP arranged to form a row in the second direction,portions of the bit line structures BLS, and portions of the word linesWL of FIG. 1.

Referring to FIG. 19, the semiconductor device 1 includes the word linesWL, the bit line structures BLS, the first contact plugs BC, and thesecond contact plugs LP.

The second contact plugs LP may be arranged to form the row in thesecond direction (direction y) which is perpendicular to the firstdirection (direction x). The second contact plugs LP may be arranged tooverlap corresponding side surfaces BLS-L of adjacent bit linestructures BLS.

Although it is illustrated in FIG. 19 that the second contact plugs LPare arranged to overlap the left side surfaces BLS-L of the bit linestructures BLS, the second contact plugs LP may be arranged to overlapthe right side surfaces BLS-R of the bit line structures BLS, asillustrated in FIG. 1.

FIG. 20 is a layout of some elements of the semiconductor device 1. Indetail, FIG. 20 is a layout of portions of the body portions LP1 of thesecond contact plugs LP and the plurality of active areas ACT of FIG. 1.

Referring to FIG. 20, the semiconductor device 1 includes the pluralityof active areas ACT, the first contact plugs BC, and the second contactplugs LP.

A column formed by the body portions LP1 along an extension lineconnecting the body portions LP1 may be arranged along a direction thatis different from a direction of the major axis ACT-LX of the activearea ACT.

The major axis ACT-LX of the active area ACT may have a first angle θ1with respect to the first direction (direction x). The column formed bythe body portions LP1 may extend by an angle that is greater than thefirst angle θ1, with respect to the first direction (direction x).

The extension line connecting the body portions LP1 is along the samedirection as a direction in which the second line patterns 320 of 9Bextend. Accordingly, the extension line may extend by a third angle θ3with respect to the first direction (direction x), and the third angleθ3 may be greater than the first angle θ1.

FIG. 21 is a block diagram of the semiconductor device 1.

Referring to FIG. 21, the semiconductor device 1 includes a memory cellarray 10, a row decoder 20, a sense amplifier 30, a column decoder 40, aself-refresh control circuit 50, a command decoder 60, a mode registerset/extended mode register set (MRS/EMRS) circuit 70, an address buffer80, and a data input/output circuit 90.

A plurality of memory cells for storing data are arranged in a row andcolumn direction in the memory cell array 10. The plurality of memorycells may be each formed of a cell capacitor and an access transistor. Agate of the access transistor may be connected with a corresponding wordline from among a plurality of word lines arranged in the row direction.One of a source and a drain of the access transistor may be connectedwith a bit line BL or complementary bit line (/BL) arranged in thecolumn direction, and the other may be connected with the cellcapacitor. FIGS. 1 and 2 may correspond to the memory cell array 10 ofthe semiconductor device 1.

The sense amplifier 30 detects and amplifies data of the memory cell andstores the data in the memory cell. The sense amplifier 30 may berealized as a cross-coupled amplifier connected between the bit line BLand the complementary bit line /BL.

Data DQ input via the data input/output circuit 90 is written in thememory cell array 10 based on an address signal ADD, and data DQ readfrom the memory cell array 10 based on the address signal ADD is outputvia the data input/output circuit 90. The address signal ADD is input tothe address buffer 80 to designate the memory cell to/from which thedata is to be written/read. The address buffer 80 temporarily stores theaddress signal ADD.

The row decoder 20 decodes the row address output from the addressbuffer 80 and enables a corresponding word line in a data writing orreading mode. Also, the row decoder 20 decodes the row address generatedfrom an address counter and enables a corresponding word line in aself-refresh mode.

The column decoder 40 decodes a column address among the address signalADD output from the address buffer 80, to designate a bit line connectedwith the memory cell to/from which data is to be input/output.

The memory cell array 10 outputs data or writes data from/to the memorycell designated by the row and column addresses.

The command decoder 60 receives a command signal CMD applied from theoutside and decodes the signal to generate a decoded command signal,such as a self-refresh entry command and a self-refresh exit command.

The MRS/EMRS circuit 70 sets a mode register inside the MRS/EMRS circuit70 in response to an MRS/EMRS command and the address signal ADDdesignating an operation mode of the semiconductor device 1.

In addition, the semiconductor device 1 may further include a clockcircuit for generating a clock signal and a power circuit for receivinga power voltage applied from the outside to generate or distribute aninner voltage.

The self-refresh control circuit 50 controls a self-refresh operation ofthe semiconductor device 1 in response to the command output from thecommand decoder 60.

The command decoder 60 may include an address counter, a timer, and acore voltage generating unit. The address counter may generate a rowaddress for designating a row address which is to be the subject of theself-refresh operation and apply the row address to the row decoder 20,in response to the self-refresh entry command output from the commanddecoder 60. The address counter may end the counting operation inresponse to a self-refresh exit command output from the command decoder60.

The memory cell array 10 and the sense amplifier 30 may form a memorycore unit.

FIG. 22 is a diagram of a system 1000 including the semiconductor device1.

Referring to FIG. 22, the system 1000 includes a controller 1010, aninput/output device 1020, a memory device 1030, and an interface 1040.The system 1000 may be a system for transferring or receiving in amobile system. In some embodiments, the mobile system may be a personaldigital assistant (PDA), a portable computer, a web tablet, a wirelessphone, a mobile phone, a digital music player, or a memory card. Thecontroller 1010 is for controlling execution of a program included inthe system 1000, and may be a microprocessor, a digital signalprocessor, a microcontroller, or a similar device. The input/outputdevice 1020 may be used to input or output data of the system 1000. Thesystem 1000 may be connected with an external device, such as, apersonal computer (PC) or a network, by using the input/output device1020, and may exchange data with the external device. The input/outputdevice 1020 may be, for example, a keypad, a keyboard, or a display.

The memory device 1030 may store code and/or data for the operation ofthe controller 1010, or may store the data processed by the controller1010. The memory device 1030 includes semiconductor devices according toembodiments of the inventive concept. For example, the memory device1030 includes the semiconductor device 1 described with reference toFIGS. 1 through 20.

The interface 1040 may be a data transfer path between the system 1000and other external devices. The controller 1010, the input/output device1020, the memory device 1030, and the interface 1040 may communicatewith one another via a bus 1050. The system 1000 may be used in a mobilephone, an MP3 player, a navigation device, a portable multimedia player(PMP), a solid state disk (SSD), and household appliances.

FIG. 23 is a diagram of a memory card 1100 including the semiconductordevice 1.

Referring to FIG. 23, the memory card 1100 includes a memory device 1110and a memory controller 1120.

The memory device 1110 may store data. In some embodiments, the memorydevice 1110 may have a non-volatile characteristic which may retainstored data even if a power supply is removed from the memory device1110. The memory device 1110 includes semiconductor devices according toembodiments of the inventive concept. For example, the memory device1110 includes the semiconductor device 1 described with reference toFIGS. 1 through 20.

The memory controller 1120 may read data stored in the memory device1110 or store data in the memory device 1110 in response to a read/writerequest of a host 1130.

While the inventive concept has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

What is claimed:
 1. A semiconductor device comprising: a substratehaving a plurality of active areas; a plurality of bit line structuresformed on the substrate, each comprising a bit line extending in a firstdirection and a bit line spacer layer extending along two opposing sidesurfaces of the bit line; a plurality of contact holes spaced apart fromone another in a lengthwise direction in a space between ones of theplurality of bit line structures; a plurality of first contact plugsfilling respective bottom portions of the plurality of contact holes andelectrically connected with respective ones of the plurality of activeareas; and a plurality of second contact plugs electrically connectedwith respective ones of the plurality of first contact plugs, theplurality of second contact plugs being placed in a zigzag row along thefirst direction, and each comprising a body portion and an extensionportion extending from the body portion into a respective one of theplurality of contact holes, wherein the body portions of two of theplurality of second contact plugs that correspond to one of theplurality of active areas, have different size areas that overlap acorresponding one of the plurality of active areas.
 2. The semiconductordevice of claim 1, wherein a plurality of body portions are alternatelyarranged to alternately overlap two opposing side surfaces of one of thebit line structure in the first direction.
 3. The semiconductor deviceof claim 1, wherein each body portion overlaps a portion of a respectiveone of the plurality of bit line structures and overlaps a portion of arespective one of the plurality of contact holes, in a directionperpendicular to a main surface of the substrate.
 4. The semiconductordevice of claim 1, wherein the body portions of two of the plurality ofsecond contact plugs that correspond to one of the plurality of activeareas, are arranged on different ones of the plurality of bit linestructures.
 5. The semiconductor device of claim 4, wherein the bodyportions of two of the plurality of second contact plugs that correspondto one of the plurality of active areas, are arranged such that the bodyportions overlap side surfaces of an identical direction of thedifferent bit line structures.
 6. The semiconductor device of claim 1,wherein column portions of an extension line connecting two bodyportions corresponding to one of the plurality of active areas, isarranged along a different direction from a direction of a major axis ofthe one of the plurality of active areas.
 7. The semiconductor device ofclaim 1, wherein each of the plurality of active areas has a major axisextending along a direction diagonal with respect to the firstdirection, and two body portions corresponding to one of the pluralityof active areas, overlap an identical side surface of the one of theplurality of active areas, the two opposing side surfaces of the bitline being based on the major axis.
 8. The semiconductor device of claim1, wherein the plurality of second contact plugs are arranged to form acolumn along a second direction which is perpendicular to the firstdirection, and the plurality of second contact plugs arranged in thecolumn are arranged to overlap different side surfaces of the pluralityof bit line structures oriented in an identical direction.
 9. Thesemiconductor device of claim 1, further comprising a plurality ofstorage nodes each formed on the plurality of second contact plugs,respectively, and laid out in the hexagonal array structure with respectto a main surface of the substrate, wherein respective areas of lowersurfaces of the plurality of storage nodes are greater than areas ofrespective upper surfaces of the plurality of second contact plugs. 10.The semiconductor device of claim 1, wherein two of the plurality offirst contact plugs corresponding to one of the plurality of activeareas, have symmetrical positions with respect to a center of the one ofthe plurality of active areas, and two of the plurality of secondcontact plugs corresponding to one of the plurality of active areas,have asymmetrical positions with respect to the center of the one of theplurality of active areas.
 11. The semiconductor device of claim 1,wherein each of the second contact plugs has a diamond-shapedcross-sectional plane, and wherein the diamond-shaped cross-sectionalplane is included in the body portion.
 12. The semiconductor device ofclaim 11, wherein a diagonal line of the body portion with respect tothe diamond-shaped cross-sectional plane extends in the first direction.13. The semiconductor device of claim 12, wherein lengths of twodiagonal lines of the body portion with respect to the diamond-shapedcross-sectional plane are different from each other.
 14. Thesemiconductor device of claim 11, wherein the cross-sectional plane ofthe body portion has a round-edged diamond shape.
 15. The semiconductordevice of claim 13, wherein three of four edges of the diamond-shapedcross-sectional plane of the body portion overlap the respective one ofthe plurality of bit line structures.
 16. A semiconductor devicecomprising: a substrate having a plurality of active areas; a pluralityof bit line structures formed on the substrate, each comprising a bitline extending in a first direction and a bit line spacer layerextending along two side surfaces of the bit line; a plurality of firstcontact plugs spaced apart from one another in a lengthwise direction ofa space between ones of the plurality of bit line structures, andelectrically connected with respective ones of the plurality of activeareas; and a plurality of second contact plugs electrically connectedwith respective ones of the plurality of first contact plugs and onrespective ones of the plurality of bit line structures, wherein theplurality of second contact plugs overlap respective portions of theplurality of bit line structures and respective portions of theplurality of first contact plugs in the direction perpendicular to themain surface of the substrate, and respective portions of the pluralityof second contact plugs, which are arranged on upper surfaces of therespective ones of the plurality of bit line structures to have an areathat overlaps the plurality of bit line structures, which is greaterthan an area thereof overlapping the plurality of first contact plugs.17. The semiconductor device of claim 16, wherein the two from among theplurality of second contact plugs, corresponding to the one from amongthe plurality of active areas, are arranged on two adjacent bit linestructures, respectively.
 18. The semiconductor device of claim 16,wherein a cross-sectional plane of the second contact plugs on uppersurfaces of the plurality of bit line structures has a round edgeddiamond shape.
 19. A semiconductor device comprising: a substrate havinga plurality of active areas; a plurality of bit line structures formedon the substrate, each comprising a bit line extending in a firstdirection and a bit line spacer layer extending along two opposing sidesurfaces of the bit line; a plurality of contact holes spaced apart fromone another in a lengthwise direction in a space between ones of theplurality of bit line structures; a plurality of first contact plugsfilling respective bottom portions of the plurality of contact holes andelectrically connected with respective ones of the plurality of activeareas, each of the plurality of first contact plugs having a firstplanar center; a plurality of second contact plugs electricallyconnected with respective ones of the plurality of first contact plugs,the plurality of second contact plugs each comprising a body portion andan extension portion extending from the body portion into a respectiveone of the plurality of contact holes, the body portion having a secondplanar center; and a plurality of storage nodes connected withrespective ones of the plurality of second contact plugs, each of theplurality of storage nodes having a third planar center; wherein thethird planar center is offset from the first planar center and the thirdplanar center is aligned with the second planar center.
 20. Thesemiconductor device of claim 19, wherein the first planar center andthe third planar center are staggered from each other in a seconddirection which is perpendicular to the first direction.